AutoCAD and BricsCAD share many system variable names. System variables are responsible for controlling the behavior of the AutoCAD and BricsCAD. There is a dialog called the System Variable Editor that you can use to access these variables. This tool can be found in the Tools panel of the Express Tools ribbon or by typing SYSVDLG at the command.
System Variables Editor in AutoCAD
System Variables Editor in BricsCAD
The System Variables Editor allow you to reset values of variables, identify default settings, and get an explanation of what each variable represents.
Sometimes system variable values that affect selection may change inexplicably. When that happens, the new setting can be quite bothersome creating an interruption to our workflow.
PICKADD controls whether are not you can make multiple, subsequent selections in a command. If you find you can no longer do this, set this variable to 2.
PICKAUTO controls automatic window selection i.e. initiating a window or crossing selection by picking the screen or dragging while the pick button is pressed. This is a bit-code setting which means there are several options and the options you want to turn on are the sum of their values. For example, the default setting for PICKAUTO is 5 which allows us to begin a window or crossing selection if the cursor is not directly over an object when you click (value=1); this also allows us to begin a window or crossing lasso selection if the cursor is not directly over an object when you click and drag (value=4).
PICKDRAG controls the method of drawing a selection window. The default value is 2 which lets you define selection windows and crossings with two clicks and lassos by clicking and dragging. If either is not working, check the value of this variable.
Here are some fun ones.
CROSSINGAREACOLOR allows you to change the background color of your crossing selection area.
WINDOWSAREACOLOR allows you to change the background color of your window selection area.
There are thousands of variables that turn on or off features, reset the behavior of the program, or optimize system performance. These variables with their settings can be tracked down by searching the online help.